Mineral grinding aids



United States Patent 43,976 MINERAL GRINDING AIDS Vance H. Dodson, Needham, and Frank G. Serafin, Peabody, Mass., assignors to W. R. Grace & Co., Cambridge, Mass., a corporation of Connecticut No Drawing. Filed Oct. 14, 1965, Ser. No. 496,144

Int. Cl. C04b 7/52 US. Cl. 10690 3 Claims ABSTRACT OF THE DISCLOSURE In the grinding of minerals (e.g., Portland cement) an additive which can be morpholine, N-methylmorpholine or a byproduct from the continuous commercial production of heterocyclic amines consisting predominantly of 4- (Z-aminoethoxy) ethylmorpholine, 2-(4-morpholethoxy) ethanol, and bis-2-(4-n1orpholinyl) ethyl ether is added to increase the efficiency of the grinding operation.

This invention relates to grinding minerals, and more particularly to the use of an additive for improving the efficiency in grinding minerals and improving the pack set characteristics of minerals.

At some stage in the processing of minerals, a grinding operation is generally necessary in order to reduce the particular mineral to a relatively small particle size. It is desirable in this grinding step to have as efficient an operation as possible, that is, to reduce the mineral to the desired particle size at a relatively rapid rate.

A grinding aid is employed to promote an increase in efiiciency, either by increasing the rate of production or by increasing the fineness of the particles at the same rate of production without having adverse effects on any of the properties of the ground product.

Cleavage of the particles during grinding of the minerals exposes fresh or nascent surfaces which have high energies due, probably, to the breaking of ionic bonds. The surface forces of the ground particles persist for some time after grinding and lead to compaction or pack set and/ or poor fluidity if they are not reduced. Mineral particles when compacted by vibration; e.g., when transported in a hopper car, often become semi-rigid and will not flow until considerable mechanical effort has been applied to break up the compaction. On the other hand, undue reduction or the complete absence of surface forces is undesirable because the finely ground mineral becomes excessively fluid.

The term pack set as used herein is intended to refer to the agglomeration or adhesion of particles by, e.g., storing or transporting in bulk. Adhesion results from sur face forces, the majority of which are created during the grinding 0f the minerals. Pack set index is a relative term which numerically indicates how prone a particular material is to start flowing after it is stored or transported in bulk. Pack set index ratio is the relative pack set index of the untreated sample compared to the treated sample. This ratio is used to permit comparison between different samples of the mineral.

Pack set index is determined in the following manner: 100 grams of the mineral is placed in a 250 milliliter Erhlenmeyer flask set on top of a variable vibrator. The flask containing a mineral is vibrated seconds after which time it is removed from the vibrator and fed into a jig with the axis of the flask lying horizontally. The flask is then rotated about its axis until the mineral which is compacted on the bottom of the flask collapses. The flask is twisted by turning at 180 angles at approximately 100 twists per minute. The number of 180 twists required for the mineral sample to collapse establishes the pack set "ice index. Thus, the greater the energy requirement to break up the bed, the higher will be the pack set index.

An additive has now been found which will function as a grinding aid and a pack set inhibitor for minerals. The novel additive of the present invention may be represented by the formulae:

(13) prs and 7' (0) Y--Rn wherein R is an alkaryl or aryl radical; R is hydrogen or an alkyl radical; R is hydrogen, hydroxyl, alkyl or aryl radical; R is hydrogen, alkyl, alkoxy or alkylhydroxy radical;

is pyrrolidyl, pyrrolyl, morpholinyl, morpholino or piperidyl radicals; Y is pyridyl, piperadyl, pyrimidinyl and pyradazinyl; R is halogen, hydroxy or an alkyl radical; and n is an integer from 0 to 5, inclusive.

R is preferably alkylphenyl or phenyl radical. It should also be understood that the aryl radical may contain substituents such as halogen, e.g., chlorine and bromine, alkyl, amino or hydroxyl radicals. The alkyl groups represented by R, R R and R are preferably lower alkyl, i.e., l to 6 carbon atom alkyl radicals. The terms pyrrolyl, pyrrolidyl, morpholino, morpholinyl and piperadyl, as used therein are intended to include the substituted radicals which are known to the art, e.g., N-methylmorpholino, and 4-(2-aminoethoxy) ethylmorpholine.

The additives of Formulae B and C are particularly preferred because of the particularly advantageous pack set properties as well as the increased grinding efliciency achieved with these classes of materials.

As illustrative of additives within the scope of the present invention, mention may be made of the following:

Aniline Piperidine p-toluidine Pyrrole M-phenylenediamine Pyrroline' Dimethylaniline Pyrrolidine Diphenylamine Pyridazine 2,4,6-tribromoaniline Pyrimidine N-phenylhydroxylamine N-methylrnorpholine Beta-phenethylamine' Dimethylpyridine Morpholine Dimethylethylpyrrole Pyridine Piperazine The additive is interground with the mineral in the grinding mill to provide increased grinding efficiency as well as other advantageous results, e.g., inhibiting pack set of bulk stored materials or inhibiting the formation of foam in some mineral processing applications. It has also been found that the novel additive of the present inven tion also serves to provide fluidity to the ground minerals when they are being transported by conveying systems, particularly by pneumatic air systems.

The term mineral as used herein is intended to refer to naturally occurring inorganic minerals, such as phosphate rock, partially processed minerals such as concentrated iron ore, and mixtures of minerals such as cement clinker or ceramics.

Further examples of such minerals which can be processed with the additive of the present invention, mention may be made of beryllium oxide, limestone, gypsum, clays, and bauxite.

The additive of the present invention is particularly preferred for use with cement, and cement-forming materials particularly portland cement.

Portland cement represents a class of hydraulic cements and is comprised essentially of two calcium silicates and a lesser amount of calcium aluminate. These cements are In a particularly preferred embodiment the additive employed is morpholine and morpholinyl derivatives. Various grades and purities of the morpholine compounds are employed with satisfactory results. A particularly preferred source of morpohline type compounds is a byproduct produced by heating an intimate mixture of finely divided 5 from the continuous commercial production of heterocalcareous material (limestone) and argillaceous material cyclic amines. The by-product contains a mixture of (clay) to fusion to form a clinker. The clinker is ground aliphatic and heterocyclic monoand diamines. The morwith the addition of about 5% gypsum, or some other pholinyl ring, however, is the dominant group present. form of calcium sulfate, to obtain the desired setting Table 3 shows a typical analysis of a by-product which qualities in the finished cement. It is to the clinker that is predominantly a mixture of 4-'(2-aminoethoxy) ethylthe novel additive of this invention is preferably added to morpholine, 2(4-morpholylethoxy) ethanol and bis-2-(4- increase grinding efiiciency and to inhibit subsequent pack morpholinyl) ethyl ether. set in the finished cement. Table The additives of the present invention are employed in either dry or liquid form. For convenience, the additive Tit atable amine Meq./g 7.52 is in liquid form to permit accurate metering into the Primary amine Meq./g 1.66 mineral stream. In instances where the additive is not Tertiary amine Meq./g 4.57 very soluble in water, it can be utilized by emulsifying it Total nitrogen Meq./g 7.93 with a suitable wetting agent, e.g., sodium dodecyl ben- Total acetylatable material Meq./g 7.02 zene sulfonate. The addition is accomplished either prior Specific gravity 20/20 C-.. 1.078 to the grinding or the additive is introduced into the grind- Water content wt. percent-.. 0.08 ing mill simultaneously with the mineral. If the additive In Table 4 the grinding emciency and pack Set data employeq nierely for reductlon of set fluldlzmg of the additive of Table 3 is reported. The data was colpurposejs 1t '15 added at any convement pomt m the lected using a Type I cement clinker and gypsum ground Processing. in a laboratory mill at 210 F. for 7411 mill revolutions.

The additive of the present invention is employed as the sole grinding aid or with a mixture of one or more TABLE 4 grinding aids or with additives known to the art other Amountotadditive (percent Blaine surface than grinding aids, e.g., set retarders or accelerators, in mud smd) Pack Set index the case of cement. Bgmk a, 441 12. 0 The additive is employed effectively over a relatively 5 36o5 L0 wide range. The preferred range is about 0.001 to 1%, r m the a ve table it can be seen that the use of d more f bl bo t 0,005 to abo t 01% b sed on even a very small amount of additive results in an increase the weight of the mineral, i.e., weight of additive solids in grinding efficiency of about 164 units as Well s a based on weight of mineral solids (herein referred to as stantial decrease in pack set index. solids on solids). In a particularly preferred embodiment The novel additive described in Table 3 was also used about 0.05% of the additive based on the weight of the to grind phosphate rock. After grinding phosphate rock mineral is employed. The higher levels are employed if with 0.03% of the additive described in Table 3 in a grinding toa relatively high surface area, and the amount 40 laboratory mill for 3752 revolutions at 200 F., 61% of additive used in limited only by the desired surface of the ground product passed a 200 mesh screen whereas area. and fluidity of the finished product. only 54% of a control sample (no additive) passed a In Table 1 the eifectiveness of the additives as grind- 200 mesh screen. ing aids is reported- The data mPorted was ai using In addition to using the above described amine coma yp 1 cement clinker gypsum ground In a pounds per se as mineral additives, the reaction product 'y mill a temperature of 7411 of the amines and an aliphatic organic acid having 2 to revolutions- 20 carbon atoms are also employed as additives and pro- TABLE 1 vide enhanced grinding efiiciency, The product is prepared m t I by the addition of acid, preferably glacial acetic acid ggg g mamesurfamma, to cause the pH to drop to not less than about 7. In a Additive solid on sol d) /spreferred embodiment the pH is lowered to about 8. The 3,441 acetylated amine acetate is produced by the addition of 3-8; Egg acid anhydride to the amine instead of the acid. 31480 The following table illustrates the use of the reaction 38% 2% product of the amine described in Table 3 and acetic acid 3:542 (pH 8) in grinding cement clinker. The Type 1 cement 3-8? 238 clinker and gypsum were ground for 4095 revolutions in 01 550 a laboratory mill heated to 200 F.

TABLE 5 In Table 2, pack set data is reported on cement inter- Air ground with the additives of this inventioniiii iii iiii i giid) i iliiifi ifi Pack set index ns i ii biiis TABLE 2 Blank 3,590 0 10.0 0.058 3,850 0 10.3 Additiofisgle Additive (Ween solid) Pack set; index From Table 5 it can be seen that the grinding efficiency Blank 12 6 and pack set properties are increased and no air is en- Anilinez 0. 05 10: 0 trained. gif 8-8; As stated above, the present invention is also directed N-metliyl morpholine 0: 01 11:3 7 to mixtures of additives. A particularly preferred mixture P'wgindme 3-8; 5% is prepared from the amine described in Table 3, tri- 0101 s10 ethanolamine and acetic acid. A preferred source of tri- 3:8? g g ethanolamine is the residue product obtained in produc- Diphenylamine- 0.05 7.3 tion of ethanolamines. The exact composition of the residue product varies within certain limits and, therefore the residue product may contain one or more of mono-, or diethanolamine in addition to the triethanolamine. One such residue product has the following analysi before neutralization TABLE 6 Triethanolamine percent by volume 45 to 55 Equivalent weight 129 to 139 Tertiary amine meq./gm 6.2 to 7.0 Water by weight, max 0.5 Density lbs./gal 9.49

The following table illustrates the grinding efficiencies obtained using the reaction product of acetic acid and a 5050 (by weight) mix of the amines of Table 3 and Table 6. The pH of the mixture was 8. Type I cement clinker and gypsum were ground in' a laboratory mill at 220 F.

TABLE 7 Mill Blaine surface revolutions area, cmfi/g. Pack set index Amount of additive (percent solid on solid) Another additive mix which is particularly useful in the present invention is one which contains 60% of the additive mix whose grinding data is described above in Table 7, 20% urea and 20% water. Table 8 shows the grinding data achieved by such a mixture when Type 1 cement clinker and gypsum are ground in a laboratory mill for 5092 revolutions at 220 F, with the additive used at a level of 0.04% (solid on solid).

TABLE 8 Blaine surface area, cmfl/g.

Pack set index therewith, the said additive being compounds selected from the group consisting of morpholine, N-methylmorpholine, and a byproduct from the continuous commercial production of heterocyclic amines consisting predominantly of 4-(2-amin'oethoxy) ethylmorpholine, 2-(4-morpholethoxy) ethanol, and bis-2-(4-morpholinyl) ethyl ether.

2. A composition comprising a mineral and intimately admixed therewith, from 0.001 to 1% based on the weight of the mineral of a mixture of (1) an aliphatic organic acid having 2-20 carbon atoms, (2) a residue product of ethanolamine synthesis, and (3) a compound selected from the group consisting of morpholine, N-methylmorpholine, and a byproduct from the continuous commercial production of heterocyclic amines consisting predominantly of 4-(2-aminoethoxy) ethylmorpholine, 2-(4- morpholylethoxy) ethanol, and bis-2-(4-rnorpholinyl) ethyl ether, said residue product being predominantly triethanolarnine and having the following properties before neutralization:

Triethanola-mine 45 to by volume Equivalent weight 123 to 139 Tertiary amine 6.2 to 7.0 meq./ gm. Water 0.5% by weight, max. Density 9.49lbs./ga1.

the proportions of (2) and (3) being equal parts by weight, and the proportion of acid being sufiicient to bring the pH of the mixture to 8.

3. The composition of claim 1 wherein the mineral is portland cement.

References Cited UNITED STATES PATENTS 2,857,286 10/1958 Striker 106-102 3,042,718 7/ 1962 Evans et a1. 252-384 3,088,837 5/ 1963 Prescott 106308 3,278,269 10/ 1966 Ekker 252384- 3,305,491 2/ 1967 Oster 252384 3,325,105 6/ 1967 Veltman 1-O6102 3,329,517 7/1967 Dodson et a1 106-315 TOBIAS E. LEVOW, Primary Examiner.

SAMUEL E. MOTT, Assistant Examiner.

US. Cl. X.=R. 

